International Patent Publication WO96/29375 discloses a process for producing an anti-fog element by supporting anatase type TiO2 film particles having a photocatalytic property on a conjugation material such as silica to obtain the anti-fog element at a low temperature of from normal room temperature to 150° C. Specifically, a suspension including anatase type TiO2 (titania) particles or rutile type TiO2 (titania) particles and silica (SiO2) particles is applied onto the surface of a substrate to form a photocatalyzer film comprising silica-formulated titania. By applying a mixture of an amorphous silica precursor such as tetraalkoxysilane, silanol or polysiloxane, with crystalline titania sol onto the surface of a substrate, optionally carrying out hydrolysis to form silanol, and then heating the system at a temperature of not less than 100° C. to perform the dehydration polycondensation of silanol, a photocatalyzer film having titania bonded to amorphous silica is formed.
However, since the photocatalyzer film just mentioned comprises the anatase type TiO2 fine particles supported only by the adhesion force to the silica film, the TiO2 fine particles are apt to be exfoliated from the surface of the film only by wiping and they injure the film.